Optical Unit Sliding Mechanism for Uniform CIS Scanning
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Solution Overview
Problem
Image reading devices using the CIS method face challenges in maintaining uniform image reading of non-flat original documents due to a shallow depth of field, requiring precise adjustments and complex structures to compensate, while devices using the CCD method are costly and complex.
Innovation Solution
An image reading device with an optical unit that includes a sliding part, pinching parts, and a biasing member, allowing the optical unit to slide on a rail part, maintaining constant distance to the document and using a driving device for sub-scanning motion, which optimizes image reading by pinching the rail from both sides and adjusting its center of gravity for stable scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the CIS method is used for image reading, then the device structure is simplified and cost is reduced, but the depth of field becomes shallow making it difficult to uniformly read non-flat documents
Solution Approach 1:
The patent implements a movable optical unit that can dynamically adjust its position along the sub-scanning direction. The optical unit is mounted on a carriage that travels along a guide shaft, allowing the focal distance to be dynamically changed as the scanner moves across the document, thereby maintaining focus on non-flat surfaces throughout the scanning process
Solution Approach 2:
The patent changes the parameter of focal distance by moving the optical unit along the sub-scanning direction. The driving mechanism (timing belt or rack and pinion) enables precise control of the optical unit's position, thereby adjusting the focal distance to match the document surface height variations and maintain uniform image reading quality
2Manufacturing precision
If the CCD method is used for image reading, then the depth of field is deep and non-flat documents can be easily read, but the device structure becomes complicated and cost increases
Solution Approach 1:
The patent replaces the complex optical system of CCD (which requires mirrors and lenses to achieve deep depth of field) with a simpler CIS-based mechanical solution. Instead of using complex optics to achieve deep depth of field, the patent uses a movable carriage mechanism to physically adjust the scanner position, achieving the same effect with simpler, more cost-effective components
Solution Approach 2:
The patent extracts and removes the unnecessary mirrors and complex optical components from the scanning system by adopting CIS technology. The solution takes out the complex optical path required by CCD and replaces it with a direct-contact or near-contact CIS sensor mounted on a movable carriage, thereby simplifying the overall device structure while maintaining image reading capability
3Area of stationary object
If the optical unit is moved in sub-scanning direction to read images, then image reading coverage is improved, but vibrations occur reducing scanning precision
Solution Approach 1:
The patent employs a bearing mechanism that supports the optical unit's weight and provides smooth guidance along the guide shaft. The bearing acts as a counterbalancing support system that reduces friction and vibration during the movement of the optical unit, thereby maintaining scanning precision while enabling full coverage image reading
Solution Approach 2:
The patent introduces a timing belt or rack and pinion mechanism as an intermediary between the driving motor and the optical unit. This intermediary transmission system smoothly transfers motion while reducing shocks and vibrations, ensuring precise and stable movement of the optical unit across the entire document area without compromising scanning accuracy
Data Source
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AI summary
An optical unit (70) of an image reading device (6) has the center of gravity in a position toward a first sub scanning direction, relative to the middle point of the optical unit (70) in terms of sub scanning directions. An engagement part (63a) is provided in a position toward a first main scanning direction relative to a sliding part (65b). A plurality of pairs of pinching parts (65c) include a first pair provided in a position toward the first sub scanning direction and a second pair provided in a position toward a second sub scanning direction. Of the two pinching parts (65c) in the second pair, the pinching part (65c) provided in a position toward the first main scanning direction is biased by a first biasing member (69) toward a rail part (80) side, and the pinching part (65c) provided in a position toward a second main scanning direction is not biased by the first biasing member (69).